Developments in router technology have led to system designs that provide a general-purpose connection-oriented transfer mode for a wide range of services. These services include the simultaneous transfer of integrated traffic (data, voice, and video traffic) over the same network system. Prior art systems have typically relied on two connections types, a switched virtual connection and a permanent virtual connection, to support the transfer of different services over the same network.
The switched virtual connection (“SVC”) relies on control protocols initiated by a physical interface to establish connections across a network. Specifically, an originating device uses control protocols to request a network connection between the originating device and the destination device. Typically, in an SVC, intermediate nodes of the network use the physical (and logical) address of the originating device to create a virtual path between the originating device and the destination device. Once the call is terminated, however, the virtual path is removed. The removal of the virtual path allows for the creation of additional virtual paths, thus increasing transmission bandwidth across the network.
In contrast, a permanent virtual connection (“PVC”) uses initial network management to establish a permanent link between two nodes. The PVC provides a stable transmission path that ensures dedicated connectivity between two nodes. The PVC, however, reduces transmissions bandwidth because, unlike the SVC, the PVC assumes control of a subset of transmission links for an indefinite period of time. Additionally, the PVC reduces the availability of transmission ports in both the originating device and the destination device.
Examples of a PVC include analog private phone lines, digital private phone lines, a direct connection between two private branch exchanges (“PBXs”,) or Frame Relay Forum (“FRF”) protocols that deal exclusively with permanent calls—such as the FRF.11 protocol. Examples of a SVC include a telephone to telephone call predicated by a dialing sequence to request a connection and asynchronous transfer mode (“ATM”) networks that use a cell-based switching and multiplexing technology to provide services for both local area networks and wide area networks. Regardless of the connection service used (SVC or PVC), prior art network systems typically use a physical port and a routing system to connect to a transmission network.
FIG. 1 shows a prior art voice port coupled to a network. In particular, system 100 includes a voice port (105), also referred to as a physical port, coupled to a routing system (105a). As illustrated in FIG. 1, voice port 105 is coupled to phone 110 via physical interface (“PI”) 115. PI 115 is responsible for multiplexing the control and audio signals of phone 110 to lines 115a and 115b, respectively.
The control signals are routed to telephony protocol 120. Using the phone 110 control signals, telephony protocol 120 negotiates with other voice ports through a call management control (not shown) to gain access to routing system 105a. Provided voice port 105 has access to routing system 105a, telephony protocol 120 transmits the control signals to routing system 105a via C127. Routing system 105, in turn, uses the control signals to establish a connection with a remote physical device. For example, if phone 110 is used to generate a SVC to a remote phone. The on-hook and off-hook signals of phone 110 denote control signals used to initiate a SVC connection. Additionally, the numbers dialed by phone 110 are control signals used to select a termination point of the SVC. Furthermore, the ringing tone, or alternatively the busy tone, transferred back to telephony protocol 120 via network 145 denotes the remote phone's response to the connection attempts by phone 110.
Following the previous example, once the control signals have established a connection with the remote device, the audio signals of phone 110 are routed to voice compression block 125. Voice compression block includes a digital signal processor (“DSP”) device that converts the audio signals into a digitized voice payload. The digital voice payload, in turn, is transferred to routing system 105a via line V126.
Routing system 105a is used to format both the control signals and the digitized data generated by voice port 105. The formatted data is subsequently transferred to a remote device via network 145. Network 145 comprises an ATM or Frame Relay network. Accordingly, routing system 105a generates packet data for transmission along network 145. In particular, packet routing 130 selects a digitized payload from either voice port 105 or other voice ports (not shown) coupled to routing system 105a. The selected digitized payload is transferred to packet encapsulation 135. In packet encapsulation 135, based on the protocol of network 145, packets are generated from the digitized payload. Additionally, in packet encapsulation 135 packet addressing information and packet headers are append to the generated packets. Subsequently, the packets are transferred to network interface (“NI”) 140 for transmission over network 145. Typically, NI 140 includes a serial interface or ethernet connection to network 145.
System 100 provides a basic system for connecting devices in a network that uses either a SVC or a PVC. System 100, however, results in numerous disadvantages when used in a heterogeneous networking system that uses both PVC and SVC. One disadvantage results from the network requirements associated with a PVC. Specifically, in a PVC at least two physical ports are designated as PVC connections. Thus, the number of available resources for SVCs is reduced. For example, if voice port 105 is designated as the terminating point of a given PVC, voice port 105 is excluded from receiving SVCs from other remote devices. Isolating voice port 105 necessitates the addition of a second voice port to support SVCs. Another disadvantage results from the typical design of voice over packet (“VOP”) systems. VOP systems are designed to connect a limited number of voice ports to a single routing system. In a PVC/SVC networking system, however, a subset of the VOP voice ports are dedicated to PVCs. The dedicated PVCs result in a VOP with a reduced number of voice ports for SVCs.